In U.S. patent application filed Mar. 9, 1971, Ser. No. 122,453 by Cookson et al now the aforesaid United States Patent 3,814,879, there is illustrated and described various means for preventing relatively small particles entering into regions of high electrical field stress. Also, the aforesaid U.S. patent application Ser. No. 288,843, now the aforesaid United States Patent 3,852,550 sets forth the problem, which is encountered in high-voltage compressed-gas circuit-interrupters, where an effort is made to prevent relatively small insulating or metallic particles entering into the high-pressure gas storage regions, where electrodes are present at widely-different voltage levels from each other, for example, approaching 200 K.V. in magnitude.
Since the opening and closing operations of the metallic contact parts tend to generate small metallic particles, which tend to roam about in the gaseous region, it is necessary to prevent these small metallic or insulating particles from entering into the high-pressure gas storage regions, where the conducting high-voltage parts are closely spaced together, and where, obviously, high electrostatic fields are generated between such closely-spaced high-voltage metallic members. It has been proved by test that small particles, either insulating or conducting, will tend to precipitate a voltage breakdown between such high-voltage members, which are at widely-different voltage levels.
In U.S. patent application filed July 7, 1972, Ser. No. 269,691 by Dakin et al, now U.S. Patent 3,792,218, issued December 12, 1974, and assigned to the assignee of the instant application, there is illustrated a perforated support cone in FIG. 1 of said patent application, which permits free communication between the high-pressure gas within the interrupting area and the high-pressure region within the lower U-shaped high-pressure gas storage chamber, and electrical heaters, designated by the reference numeral 75 in said patent application U.S. Patent 3,792,218, heat the gas to prevent liquefaction of the gas; and the thus heated gas freely enters upwardly past the high-pressure region, and through the perforated support cone and into the contact interrupting region. The hazard results that small metallic particles will enter the perforated cone, as set forth in FIG. 1 of said patent, and drop downwardly into the lower high-pressure U-shaped gas storage region, so as to create the hazard in the U-shaped high-pressure gas storage region of possible breakdown or flashover therein.
Also, reference may be made to U.S. Pat. No. 3,596,028 issued July 27, 1971 to Kane et al., and assigned to the assignee of the instant application, for a description of the general type of interrupting structure, also utilizing a perforated support cone, and which is subject to the same problem.